It is known to provide closures comprising two substantially rigid casing members, e.g. a base and a cover, which are fitted together when the closure is formed and in which the joint between the two parts is sealed by a sealing strip in the form of an O-ring. Such closures are used for example to protect splices in telecommunications cables which may contain metallic conductors or optical fibers. Such closures must be provided with means for allowing entry of one or more cables into the closure, and for sealing the closure at the point at which the cable enters.
One way in which this has been done, as disclosed in UK patent application GB-A-2261960, is to provide an opening in the wall of the base of the closure, in the form of a recess which intersects a surface of the base which abuts against a surface of the cover of the closure. A rubber insert is provided with one or more central apertures into which a cable can be inserted. The rubber insert is then introduced into the recess, where it contacts the walls of the recess and corresponding parts of the cover and an O-ring gasket which seals between the base and the cover. The insert has a flat peripheral surface at the point at which it comes into contact with the gasket. A slot may be provided in the insert to allow it to be opened to insert a cable laterally into the central aperture. A similar system is also disclosed in European patent application EP-A-0511147.
The arrangements disclosed in GB-A-2261960 and EP-A-0511147 suffer from the problem that their seal inserts (termed "sealing gaskets" in GB-A-2261960), being formed from rubber or like elastic material, do not normally provide an adequate seal unless they are coated by hand, prior to closing the casing, with a grease or the like. This is time consuming for the installation engineer and also requires him consistently to provide an adequate coating of grease for each insert each time he installs a cable splice closure, and it is consequently unreliable. Furthermore, even with an adequate grease coating, the inserts may not provide an effective long-term seal. The rubber inserts also suffer from the disadvantage that they are unable to accommodate cables over a significant range of sizes or shapes.